2.14 Immunohistochemistry staining
Paraffin skin sections (5 µm in thickness) were deparaffinized and rehydrated, and subsequently treated with antigen retrieval solution for 6 min at 96 °C. The sections were stained with PCNA antibody (Abcam; Cat#ab29; 1:200) at 4 °C overnight, and then reprobed with goat-anti-rabbit HRP-conjugated antibody for 2 h at room temperature. All antibodies were diluted with PBS containing 1% BSA. The staining was visualized by reacting with 3, 3-diaminobenzidine (1:20) (DAB; Sigma Chemical Co., USA), and then the nuclei were stained with hematoxylin (Solarbio Science & Technology, China). Results were evaluated by Nikon Eclipse Ni light microscopy.